[music throughout]
The Trojan asteroids are found in Lagrange points,
which are these special places that lead or follow a planet in its orbit
by 60 degrees, and it's sort of where the gravitational force of the planet
and the gravitational force of the Sun all cancel out.
So if you put an object there, it will stay there for a long period
of time, basically forever.
So when we see objects there, these are objects
that we know were in place a very long time ago.
So if you just take
a random asteroid and just put it in the outer Solar System,
the gravitational force
of the four outer planets will just clear them out in a very short period of time.
So they'll basically be gone.
So the only places it turns out in the outer Solar System
where you can find stable regions are these Lagrange points.
Lucy in particular, is going to go after the Jupiter Trojans.
We're trying to see a type of object
that represents and constrains the formation of the outer planets.
And you need to go to these Lagrange points in order to see that kind of thing.
One of the really groovy
aspects of our mission is its trajectory, because we're visiting
a record number of objects like these Trojans.
And we do that with this very complicated dance, particularly in the beginning,
where we are using the earth actually as a gravitational slingshot.
So Lucy will start off in an orbit very similar to the Earth,
and then gravitational encounters with the Earth will actually pump it up.
So it gets out to the Lagrange points near Jupiter's orbit.
So if you're going to understand how planets like the Earth formed,
you have to understand how the bigger planets
which sort of dominated the whole process came to be.
And that's what Lucy is going to do.